Sun stars and light flares, used properly, can add interest to a photo. It's an effect that you don't want to overuse, but with occasional, judicious use, they can liven up an image. While it is possible to add some reasonably realistic effects after the fact with software, nothing beats the real thing produced optically.

This filter is notable because it provides the option of either four point or eight point stars, giving it more versatility than many filters. It's relatively inexpensive (I don't know about you, but I'm not inclined to spend a lot on occasional-use effects), and is decently constructed. It's optically clear enough that it won't have a hugely significant impact on the amount of light coming through, and it does not appear to cause any unexpected distortion.

A few things to note, though (not exactly complaints, but things to be aware of) --

First, it provides a pretty pronounced effect. There is nothing subtle about what this lens does. Depending on what you want to do, it may be too much. Or, it may be just right.

Second, because it's made of aluminum, it is potentially subject to binding. I'd recommend keeping a filter wrench of the proper size with you just in case.

Finally, while the turning action is smooth, it is quite tight. Even a little difficult to turn, if I'm being honest. That's probably a good thing as it means it'll stay where you set it. It may or may not loosen up over time with use.

Overall, if you're looking for a star effect, this is a good, inexpensive option to add to your camera bag.